Porous belt drying apparatus



Nov. v12, 11963 E. J. Jus'rus Poaous BELT DRYING APPARATUS Filed Jim. 25. 1961 INVENTOR. [bwe 4/ M9766 Y y.

ma, www, wwfggg# Patented Nov. 12, 1953 ICC 3,110,575 PGRUS BELT DRYING APIARATUS Edgar J. Justus, Beioit, Wis., assignor to Beloit Iron Works, Beiot, Wis., a corporation of Wisconsin Filed 1an. 25, 1961, Ser. No. 84,949 5 Claims. (Cl. 34-111) The present invention relates broadly to the art of paper making, and is more particularly directed to new and improved means for removing moisture from a felt or canvas in a paper machine dryer section.

It is known that in the dry end section of a paper machine the moisture-bearing web is directed along a serpentine path in wrapping relation with drying cylinders arranged in tiers and having the cylinders in one tier staggered with respect to the cylinders or drums in the other tier. The dryer drums are heated by steam, and the traveling web is urged against the heated drums by porous felts generally woven from cotton. In this arrangement, the web during a portion of its wrap on the drying cylinders is out of contact with the felt along the oncoming and/or ott-running sides of the drums. This results in the moisture evaporated from the web being present in the pocket defined between the felt and drying cylinder. The presence of such vaporized moisture in thepocket creates a condition of high humidity therein and as well interferes with maintenance of the desired drying temperature.

In an endeavor to purge the pocket of the vaporous product of the drying operation it has been suggested to direct pressurized heated air transversely or from one side to the other of the pocket. This technique, however, is largely ineffective with paper machines of the substantial width currently in use. Specifically, it has been found impossible to completely traverse the width of the machine with the purging air jets, and as a result, on the far side of the machine from the jet or nozzle a blanket of high humidity and reduced temperature vapor exists. This obviously results in the felt and web being in conditions of non-uniform moisture content, and impairs the overall drying ethciency by having an insulative 'effect upon the steam heated drying cylinders.

It is accordingly an important aim of the present invention to provide new and improved means for removing moisture from between drying cylinders in a paper machine.

Another object of this invention lies in the provision of vapor purging means operable upon moisture within the pocket between a dryer felt and drying cylinders and which is generally coextensive with the width of the pocket.

Still another object of this invention is to provide duct means supplied with pressurized air and located closely adjacent the pocket for directing the air into and through the felt for eiiectively purging the pocket of moisture therein.

A further object of the instant invention lies in the provision of means defining a pair of plenum chambers extending entirely across the dryer felt in relatively closely spaced relation to the pocket formed by the felt and cylinders wrapped thereby, one chamber directing pressurized air through the felt and the other chamber withdrawing the air and moisture carried thereby from the pocket.

A still further object of this invention lies in the provision of moisture removal means of the foregoing charac-O ter, and in which either or both of the plenum chambers is divided transversely into separate compartments having damper means therein and providing selective control of the moisture content in the web being dried.

An even further object of this invention is to provide a plurality of tiers of drying cylinders including an upper tier and a lower tier having a paper web trained therethrough, dryer felts 'urged against the paper web while said web is trained over the drying cylinders in the upper and lower tiers and defining with said cylinders a plurality of pockets wherein there is normally present moisture evaporated from the web, and moisture removal means extending essentially entirely across the Width of at least one of the felts and located relatively close to at least one of said pockets for directing air into and through said one of said felts to purge the moisture from said one pocket.

Other objects and advantages of the invention will become more apparent during the course of the following description, particularly when taken in connection with the accompanying drawings.

vIn the drawings, wherein like numerals designate like parts throughout the same:

FIGURE 1 is a more or less diagrammatic view of a portion of a typical dry end section of a paper machine, and which incorporates therein moisture removal means in accordance with the instant inventive concepts;

FIGURE 2 is a diagrammatic plan View, with parts thereof in section and with other parts removed, showing the present means for purging moisture from a pocket; and

FIGURE 3 is a diagrammatic side elevational view of another form of duct means and featuring therein a plurality of transversely adjacent compartments having damper means therein for selectively discharging controlled volumes of purging air.

Referring now to the drawings, in FIGURE 1 of the drawings there appears a paper machine dry end section generally designatedby the numeral 10 and comprising an upper tier of drying drums or cylinders 11a-d (the latter drum being shown only partially) and a lower tier of drying cylinders 12a-c, noted to be vertically staggered with respect to the drying cylinders 11a-d in the upper tier. The direction of travel of the rolls in each case is indicated by an arrow thereon, and it will be appreciated that a paper web' W lapped about each of the rolls 11 and 12 travels in the direction indicated by the rotation of the rolls or cylinders..

A tirst upper felt 13 passes under a guide roll 14, over a web covered top surface region of the roll 11b, under another guide roll 15, over the top web covered surface of the drying cylinder 11C, around another guide roll 16 and then away from the upper tier, as indicated by the arrow. A second upper felt 17 passes along a downwardly directed felt run 17a and around a guide roll 18 and then onto the top of the drying cylinder 11d. It will be appreciated that the second upper felt 17 then follows a course along drying cylinders successive to the drum 11d in generally the manner indicated with reference to the iirst upper felt 13.

A bottom felt 19 passes over guide rolls 20, 21, 22 and 23 and are urged against the web covered regions of the drying cylinders 12a-c. The bottom felt 19 is indicated by the arrow thereon as having a return path from the guide roll 23, although if additional drying cylinders were provided in the lower tier, the bottom dryer felt 19 would likely for a distance continue along a serpentine path.

In the typical dry end section 10 thus far described and arranged as shown solely to provide a suitable environment for the instant invention, it maybe noted that the moisture-bearing paper web W as it wraps the drying cylinders 11 andy 12, and particularly as it travels from one cylinder 11 to another cylinder 12., is out of contact with the dryer felts 13 and 19. To illustrate, and referring particularly for purposes of explanation to the drying drums 11a and 11b, the paper web W is urged by the felt 13 against the cylinder 11a from point a to `ther be observed from FIGURE 2 that point 17, and while contacting the cylinder 11a and the felt I3 moisture in the web is evaporated therefrom and passes through the porous felt and is removed from the machine room by any suitable ventilation system. However, as the web moves from the drying cylinder lla to the drying drum 12a and then to` the drying cylinder 1lb, there is no longer felt to web contact and the paper web contacts solely the heated drying surface from the point b to the point c, as applied to the web on the dryingvcylinder Ila. Likewise, from the point ci to the point e the paper web is out of felt Contact as it begins its travel about the drying cylinder lib.

Since from the point b to the point c and from the point d to the point e the web is not overlapped or covered by the felt i3, moisture remaining in the web is evaporated and proceeds outwardly from the web and collects in a pocket defined by the points stated and by the felt runs 13a and 13b. This pocket is identified by the legend P-l, and it may be noted that additional pockets are formed in the dry end section It) illustrated, and are identied therein by the legends P2, P-S and The presence of moisture in the pockets P interferes with the drying efficiency by reason of the high humidity and reduced temperature conditions created. As was stated earlier, the moisture in the pockets acts as an insulative blanket with respect to the steam heated cylinders, requiring an increased heat input, and of course, the existence of a high moisture content blanket against the traveling sheet increases Vthe drying time. In an endeavor to alleviate these conditions the prior art has positioned a nozzle or jet at one side of the pocket and endeavored to direct transversely of the felt heated and high pressured air. However, present day drying cylinders often have an axial length in excess of 200 inches, and accordingly, the energy supplied to the jet is dissipated before it can traverse the Width of the machine. Residual moisture therefore is present in the pocket and at least some of the earlier discussed difficulties remain.

To effectively clean or purge one or more of the pockets P there is provided in accordance Vwith this invention moisture removal means generally identified by the numeral Se. In FIGURE l there is shown as located relatively close to each of the pockets P moisture removal means 30, although the noted problems may be effectively eliminated by the use of only one device adjacent either or both of the felt runs i3 and i9.

The moisture removal means 30 comprises `a pair of duct membersll and 32 extending transversely across the width of either or both of the alternatively, the means 39 may be provided by a single housing having a transverse baffle therein. In any event, and as is shown, each duct member has a top wall 33, opposed end walls 34 and 35, a side wall 36, a generally horizontal .bottom wall 37, and an inclined or sloping wall 38 connecting the side and bottom walls 36 and 37. The sloping wall 38 can be seen from FIGURE 2 to be slotted along the length thereof to run 13a and 13b, and except with respect to the sloping wall 38, the duct members 3l and 32 are of closed construction.

Either or both of the end walls 34 or 35 of the duct member 31 has connected thereto conduit means 40 to which is supplied pressurized air from outlet 41a of fan or blower means 41. The air so supplied may pass over or through heating means 43 if desired, and it may furone or both of the end walls of the duct member 32 may receive conduit means 42 communicating with inlet'side dlb of the fan or blower means 4l. As will later be explained, pressurized air supplied to the duct member 31 and into and through the felt run 13a purges from the pocket felts 13 and .119, or I a P-I moisture present therein, and the purged moisture may be removed from the general area by the customary ventilation system provided in the machine room. However, in order to ventilate the pockets P and provide a continuous circulation of moisture vapors produced by the drying operation, the duct member 32, through the conduit means 42, is under the iniiuence of suction forces. In such an application wherein the pockets are ventilated or a continuous circulation of air provided therethrough, use of the heater means 43 would be indicated.

The moisture removal means 39 are supported in the location shown in any convenient manner, and the mounting means for the drying cylinders il takes the form customary in the art. Such details form no part of the instant invention and are accordingly not speciiically iilustrated, although it wiil b e seen from FIGURE 2 that the drying cylinders Ila and lib are equipped at opposite ends with hub means 4- and 45, the latter hub means communicating with a steam supply header 46 to which steam is supplied under action of pump means 47, shown diagrammatically. Steam is thereby continuously directed through the header i6 and hubs or journals 45 to the interior of the hollow drying cylinders il, and the condensate is removed therefrom in the manner well known to the art.

By the arrangement described, vaporized moisture entering the pocket P-i from the web as thc web moves from the point b to the point c is promptly purged therefrom entirely along the length thereof or transversely of the felt I3 by an air source of uniform temperature, pressure and volume. The air issuing from the nozzles 39 in the duct member 3i passes into and through the felt run and effectively cieanses or purges the pocket P-i of moisture vapors. The air and entrained moisture purged from the pocket can be removed by the conventional ventilation system in the machine room from either or both Sides of the machine, but preferably the duct member 32 is subjected to suction forces so that the purging air width entrained moisture is immediately withdrawn from the pocket P-il. The pocket is accordingly ventilated and a continuous air circulation provided between the duct members .3i and 32. The pressurized purging air is heated by the heating means 43. However, whether or not a continuous circulation is provided between the duct members 3l. and 32, by purging the pocket P-ll of water vapors uniformly across the pocket, the humidity and temperature of the air within the pocket is maintained relatively constant, with the result that the drying eiiiciency ismarkedly increased. High humidity conditions are no longer present, and accordingly, the drying capacity of the dry end section It? is also increased.

A further benefit derived from positioning the moisture removal means 3@ in the position shown and from directing into and through the felt pressurized air is that moisture absorbed in the felt from its contact with the web W between the point a and b is not only removed to a large extent, but is removed uniformly entirely across the felt. The use of the purging air for this purpose has the iirst advantage of reducing the moisture content in the felt, and doing so uniformly thereacross, before the felt advances to the next drying cylinder. The drying eiiiciency at the next cylinder is therefore improved, and as Well, the amount of moisture required to be removed from the felt by the conventional felt dryer is reduced.

Particular applications may render it desirable that the moisture removal means 30 be divided into transversely adjacent compartments the output of which are controllable as to volume. An exemplary arrangement for this purpose appears in FIGURE 3, and a duct member 50 to which pressurized air is supplied by conduit means 51 may mount therewithin a plurality of baille or divider members 52 erected from a discharge wall 53 and dividing the interior of the duct member into a plurality of transversely adjacent air supply compartments 54. The side walls (not shown) of the duct member Si) may support pin or rod means 55 supporting thereon damper means 56. The damper means 56 are shown in various illustrative positions of adjustment, and it may be noted that the central damper member is completely open, while the dampers in opposite directions across the width of the duct member progressively approach closed positions. This is illustrative only, although it may be anticipated that the conventional ventilation system in the machine room would withdraw air in greater volumes outwardly of the central portion of the duct member. In any event, by selectively adjusting the positions of the damper means the air supply to the pocket can be adjusted so that the moisture content of the web being dried can be additionally controlled in this fashion. 1n other words, the web at opposite ends of the drying cylinder generally has a lower` moisture content, and by selectively adjusting the dampers 55 to generally positions indicated an over supply of purging air is not directed at the relatively dryer ends of the paper.

1t may be seen from the foregoing that by the moisture removal means of this invention there is eliminated the problem existing in the earlier purging system of energy dissipation when it was attempted by a jet or nozzle to blow air transverse to the machine and through the pocket. T he present method of directing into and. through the dryer felt purging air of constant and uniform pressure, temperature and humidity entirely across the width of the felt assures that there will be present in the pocket no residual moisture, as for example adjacent the end remote from the prior art nozzle arrangement. The means of this invention thereby increases the drying capacity of the dry end section by precise air humidity and temperature control in the pocket. As was described, by equipping one duct member with air discharge capabilities and the other with air exhaust or suction capabilities, effective pocket ventilation is provided.

It has been noted that the moisture removal means may be located at one or a number of positions, and that the duct means may be divided into transversely adjacent compartments. It may also be noted that advantages may be obtained in the purging of the moisture laden air from the pockets, P, by employing the pumping effect of the rolls 1d, 15, or 21, 22. At higher speeds these rolls carry appreciable quantities of air toward the felt as it approaches the rolls and away from the felt it leaves the rolls. This effect is enhanced by the use of an upright plate baille coextensive with the felt rolls and in sealing relation therewith. Although significant gains may be achieved, the addition of pressure and/ or suction means is preferred for its greater effectiveness. It is accordingly believed quite apparent that numerous modifications and changes may be made in this invention without departing from the novel concepts thereof.

I claim as my invention:

1. A drying mechanism for a paper machine comprising a plurality of tiers of drying cylinders including an upper tier and a lower tier for having a paper web trained therethrough, dryer felts urged against the paper web while said web is trained over the drying cylinders in the upper and lower tiers with said cylinders in each tier forming pockets therebetween containing moisture evaporated from the web, a delivery duct means outside of said felt having a discharge extending across the felt and facing one of the pockets for forcing heated drying air through the felt into the pocket, and a removal duct means outside of said felt having an intake extending across the felt and facing said one pocket withdrawing the heated drying air mixed with moisture from the pocket.

2. A drying mechanism for a paper machine comprising a plurality of tiers of drying cylinders including an upper tier and a lower tier for having a paper web trained therethrough, dryer felts urged against the paper web while said web is trained over the drying cylinders in the upper and lower tiers with said cylinders in each tier forming pockets therebetween containing moisture evaporated from the web, a delivery duct means outside of said felt having a discharge extending across the felt and facing one of the pockets for forcing heated drying air through the web into the pocket, and a removal duct means outside of said felt having an intake extending across the felt and facing said one pocket withdrawing the heated drying air mixed with moisture from the pocket, said delivery duct being positioned ahead of said removal duct means with respect to the direction of felt travel.

3. A drying mechanism for a paper machine comprising a plurality of tiers of drying cylinders including an upper tier and a lower tier for having a paper web trained therethrough, dryer felts urged against the paper web while said -web is trained over the drying cylinders in the upper and lower tiers with said cylinders in each tier forming pockets therebetween containing moisture evaporated from the web, a delivery duct means outside of said felt having a discharge extending across the felt and facing one of vthe pockets for forcing heated drying air through the felt into the pocket, a removal duct means outside of said felt having an intake extending across the felt and facing said one pocket withdrawing the heated dry-ing air mixed with moisture from the pocket, and means for controllably varying lthe quantity of air delivered by said delivery duct means at different locations across the fe'lt `to control the drying rate at different locations.

4. A drying mechanism for a paper machine comprising a plurality of tiers of drying cylinders including an upper tier and a lower tier for having a paper web trained therethrough, dryer felts urged against the paper web while said web is trained over the drying cylinders in the upper and lower tiers with said cylinders in each tier forming pockets therebetween containing moisture evaporated from the web, a delivery duct means outside 0f Said-felt having a discharge extending across the felt and facing one of the pockets for forcing heated drying air through the web into the pocket, a removal duct means outside of said felt having an intake extending across the felt and facing said one pocket withdrawing the heated drying air mixed with moisture from the pocket, and a plurality of damper means at spaced locations across said delivery duct means adjustable to control the `air iiow at different locations to the web for controlling the drying rate at different locations across the web.

5. A drying mechanism for a paper machine comprising a plurality of tiers of drying cylinders including an upper tier and a 'lower tier for having a paper web trained therethrough, dryer felts urged `against the paper web while said web is trained over the drying cylinders in the upper and lower tiers with said cylinders in each tier forming pockets therebetween con-taining moisture evaporated from the Web, a delivery duct means outside of said felt having a discharge extending across the felt and forcing heated air through the fehlt into one of the pockets, and means for controllably varying the quantity of air delivered yby said delivery duct means at different locations across the felt to control the drying rate at different locations.

References Cited in the file of this patent UNITED STATES PATENTS 1,199,394 Liebeck Sept. 26, 1916 1,697,454 Brown et al .Jan. l, 1929 2,332,067 Ericksson Oct. 19, 1943 2,907,119 Kane Oct. 6, 19559 2,929,153 Fry Mar. 22, 1960 3,004,348 Gustafsson Oct. 17, 1961 FOREIGN PATENTS `14,660 Great Britain June 18, 1914 534,389 Great Britain Mar. 5, 1941 

1. A DRYING MECHANISM FOR A PAPER MACHINE COMPRISING A PLURALITY OF TIERS OF DRYING CYLINDERS INCLUDING AN UPPER TIER AND A LOWER TIER FOR HAVING A PAPER WEB TRAINED THERETHROUGH, DRYER FELTS URGED AGAINST THE PAPER WEB WHILE SAID WEB IS TRAINED OVER THE DRYING CYLINDERS IN THE UPPER AND LOWER TIERS WITH SAID CYLINDERS IN EACH TIER FORMING POCKETS THEREBETWEEN CONTAINING MOISTURE EVAPORATED FROM THE WEB, A DELIVERY DUCT MEANS OUTSIDE OF SAID FELT HAVING A DISCHARGE EXTENDING ACROSS THE FELT AND FACING ONE OF THE POCKETS FOR FORCING HEATED DRYING AIR THOUGH THE FELT INTO THE POCKET, AND A REMOVAL DUCT MEANS OUTSIDE OF SAID FELT HAVING AN INTAKE EXTENDING ACROSS THE FELT AND FACING SAID ONE POCKET WITHDRAWING THE HEATED DRYING AIR MIXED WITH MOSITURE FROM THE POCKET. 